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Physica C Superconductivity

Numerical study of ground state and low lying excitations of quantum antiferromagnets

Nandini Trevedi, David M. Ceperley

Published Dec 1, 1989• 0 citations
Publisher
DOI
10.1016/0921-4534(89)90769-7

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The ground-state properties and low-lying excitations of spin systems with competing interactions are studied for various finite two-dimensional S= 1 / 2 Heisenberg systems of 8 spins and corresponding Ising systems of up to 60 spins. The response of the spin systems on the conflict in the interactions is studied using numerical exact results. In the Ising model the competition of the interactions influences the ground state and the excitations essentially. Contrary to conventional Ising systems in disordered strongly frustrated Ising systems the low-energy density of states is smooth, the gap between the ground state and the first excitations vanishes. The low-lying excitations are characterised by a large portion of multiple spin excitations. Thermodynamic consequences are indicated. In the Heisenberg case the influence of the conflict in the interactions is less obvious, the character of the ground state and of the first excitation has similarities with that of conventional antiferromagnets, the spins have an enlarged number of possibilities to evade the conflict in the interactions.